1. Field of the Invention
The present invention relates to a transporting tool suitably used in a probe apparatus or the like to transport an object to be tested (e.g., wafer), and a transporting system to transport the object to be tested. More specifically, the present invention relates to a transporting tool and a transporting system which can transport even a non-fixed-form object to be tested (e.g., a cracked wafer).
2. Description of the Related Art
The present invention can be applied to various types of apparatuses to process or test an object to be tested, e.g., a wafer itself, or a plurality of semiconductor elements or liquid crystal elements formed on the wafer.
In the following description, for the sake of more practical explanation, a probe apparatus which tests individual semiconductor elements formed on a wafer will be described hereinafter.
A probe apparatus which tests individual semiconductor elements formed on the wafer is widely known. FIGS. 7A and 7B show an example of the probe apparatus. The probe apparatus has a loader chamber 1 from which a fixed-form wafer W′ is transported, and a prober chamber 2 where the electrical characteristics of the fixed-form wafer W′ transferred from the loader chamber 1 are tested. A cassette storing portion 3 where a cassette C which stores the fixed-form wafer W′ is placed, a transporting arm (to be referred to as fork hereinafter) 4 which transports the fixed-form wafer W′ to the loader chamber 1, and a sub chuck 5 are disposed in the loader chamber 1. The sub chuck 5 prealigns the position of the wafer with reference to its orientation flat while transporting the fixed-form wafer W′ with the fork 4. An object-to-be-tested stage table (to be referred to as a main chuck hereinafter) 6 where the prealigned fixed-form wafer W′ received from the fork 4 is to be placed, an aligning mechanism (to be referred to as an alignment mechanism hereinafter) 7 to accurately align the fixed-form wafer W′ on the main chuck 6, and a probe card 8 having a large number of probes 8A which come into electrical contact with the electrode pads of the fixed-form wafer W′ aligned by the alignment mechanism 7 are disposed in the prober chamber 2. The main chuck 6 has a mechanism to move in the X, Y, Z, and θ directions. The probe card 8 is fixed to a head plate 2A arranged on the upper surface of the prober chamber 2.
As shown in FIGS. 7A and 7B, the alignment mechanism 7 has a lower CCD camera 7A, upper CCD camera 7B, and control device. The lower CCD camera 7A is provided to the main chuck 6, and photographs the images of the probes 8A of the probe card 8 from below. The upper CCD camera 7B is disposed at the center of an alignment bridge (7C), and photographs the image of the fixed-form wafer W′ on the main chuck 6 from above. The photographed images of the probes 8A and fixed-form wafer W′ are displayed on a monitor screen 9A of a display device 9. The alignment bridge 7C moves from the deepest portion (the upper portion in FIG. 7B) of the prober chamber 2 to the probe center along guide rails 7D disposed above the prober chamber 2 in the Y direction. A target 7E which can move forward to above the lower CCD camera 7A and backward from it is provided to the main chuck 6. The lower CCD camera 7A photographs the images of the needle points of the probes 8A and obtains the heights of the needle points. After that, the optical axis of the lower CCD camera 7A is set to coincide with the optical axis of the upper CCD camera 7B through the target 7E. The position of the main chuck 6 at this time is used as a reference position when aligning the fixed-form wafer W′ and probes 8A.
A test head T is swingably disposed in the prober chamber 2. The test head T is electrically connected to the probe card 8 through an interface (not shown). A signal from a tester is transmitted to the electrode pads of the fixed-form wafer W′ through the test head T and probes 8A. The electrical characteristics of a plurality of semiconductor elements (to be also described as chips hereinafter) formed on the fixed-form wafer W′ are tested with this signal.
The loader chamber 1 has a wafer storing table (to be described as an unload table hereinafter) 10. The unload table 10 can be inserted in and extracted from the front surface of the loader chamber 1. The unload table 10 is used when, e.g., testing a monitor wafer W″.
As described above, when a fixed-form wafer having a predetermined diameter is to be tested, fixed-form wafers W′ are automatically extracted one by one from the cassette C in the cassette stage portion 3, and the electrical characteristics of the fixed-form wafers W′ are tested. In the manufacturing process of, e.g., semiconductor elements, a wafer may be cracked. As the cracked wafer has a diameter smaller than that of the fixed-form wafer, it cannot be stored in the cassette C or automatically extracted from the cassette C. Wafers to be tested are limited to, e.g., fixed-form wafers W′ having circular shapes or the like. Cracked wafers other than the fixed-form wafers W′ or other non-fixed-form wafers cannot be tested. For this reason, when testing a cracked wafer, the operator must open the prober chamber 2 and place the cracked wafer on the main chuck 6 manually. Software for driving a conventional probe apparatus does not cope with manual operation done by an operator. Thus, sufficient safety is not always ensured when the operator recovers a non-fixed-form wafer from the main chuck 6 manually.